Several known Distribution Automation (DA) products call for input/output (IO) extensions, flexible local I/O replacements or other additional components to offer scalability. In case of remote I/Os, meaning self-contained I/O devices connecting physical, digital/analog I/O to other DA products, the remote I/O devices should be capable of supplying specified power to connected DA products. Specified power can be supplied through use of a power supply module. The power rating of the individual power supply module can be limited by the available height, board space and by the limitation on volumetric heat dissipation. For example, a power supply module in a remote I/O device can have a capability to supply a maximum of 7.5 W, for example, but under certain conditions supply 15 W. Under this condition, two power supply modules can be connected together in parallel. Thus, to supply higher power several parallel connected power supplies can be used. In addition to higher currents, the parallel modules can also offer redundancy, an important factor to achieve reliable, uninterrupted operation and extended life expectancy in the systems.
Independent power supply modules when connected in a parallel configuration can result in each of the independent power supply modules sharing unequal loads including sinking current instead of sourcing due to differences in operating point or output V-I characteristic, even when they are of similar kind. This condition can result in uneven distribution of electrical and thermal stress, and lead to a decrease in the life of overloaded power supply module. To avoid an unbalanced sharing of load current, a known technique is to include circuitry for proportionally distributing load current among parallel connected power supply modules depending on their individual capacity. This technique is referred to as “load sharing”. Load sharing can be found in power supplies wherein more than one power module service a single load or has a common point such as on a common output voltage bus which supplies power to multiple loads. Further, the common output voltage bus should be provided in such a manner that independent power supply modules are capable of indicating their respective health status in spite of having multiple independent power supply modules connected in parallel. Each power supply module should be decoupled from any effect of having voltage output from a power supply combination be available at the output of each power supply module in the combination including that of the faulty supply.
In known implementations power supplies can use high frequency switching as a means for efficiently converting the input source to the desired DC voltage level. Power supplies can be designed to operate around a large range of high frequencies that may also generate noise capable of creating interference. The noise in power supply modules connected in parallel can result from cross talk/interference due to the coupling at the input/output and due to interaction from load sharing control loops of various modules used for proportionally distributing load current among parallel connected power supply modules. Such spreading of noise from a module across the entire system can lead to stability issues in any of the power supply modules, eventually risking the stability of the entire system. The task of controlling noise and improving stability can be challenging when there is no common input voltage source to the converter power supplies and/or the power supply modules support a wide input voltage range.
The noise and stability can be improved by effective decoupling which is achieved by reducing noise and cross talk in the system for reliable operation. Further, decoupling can also be specified for reliable health indication and communication in the system.